KR100274913B1 - Noise-cancelling telephone hanset - Google Patents

Abstract

A conventional handset and a handset or wireless or telephone handset having a handle portion connecting them are designed to have physical properties suitable for acoustic properties to complement the noise canceling circuit. The handset speaker is mounted in the handset cap, which is formed with a perforated round earpiece, which extends from the outer surface of the handset cap. The round shape of the earpiece fits into the user's outer ear to help position the handset with respect to the user's ear. Opening radially on the handset cap outer surface, the openings surrounding the earpiece define a voice grille through which signals from the handset skikers are substantially transmitted directly to the ear hole of the user. The noise absorbing material is disposed at an appropriate location in the handset.

Description

Ambient Noise Reduction Phone Handset

1 is a side view of the handset.

2 is a partial side cross-sectional view of the handset cap of the handset of the present invention.

3 is a front view of the handset cap.

4 is a graph showing the magnitude and phase delay relationship between the handset input drive voltage and the output voltage of the noise canceling microphone.

5 shows active noise canceling characteristics of an embodiment of the invention.

* Explanation of symbols for main parts of the drawings

9: telephone line 10: handset

11: handset cap 12: handset cap

13, 30: foam 14: handle portion

15: handset 16: wire

17, 25: sleeve 18, 23: housing

19: earpiece 20: outer surface

21: slot 22: microphone

24: Flange 26: Port

27: extension portion 28: pad

29: cavity 31: screen

33 passage 40: control circuit

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a telephone handset device, and more particularly, to a handset configured to improve the performance of a noise canceling circuit that reduces the energy of ambient noise that interferes with the intelligibility of an incoming voice signal.

Handsets, which are standard equipment in telephones and other communication stations, such as cellular terminals, consist essentially of the handset and the handset microphones connected by a handle portion. Using a conventional handset in noisy environments, such as construction sites, machine shops, airports, bus terminals, or car telephone stations, reduces the utility as many ambient noises interfere with the user's hearing. Thus, measures such as volume control are used in prior art talkers to improve the intelligibility of the incoming speech by increasing the incoming speech signal relative to the noise signal level. However, the unwanted noise still flows into the user, and the resulting signal-to-noise ratio still results in significant interference with speech clarity.

Prior art handsets typically did not use noise canceling circuitry, but such circuits can be found in, for example, prior art handsets used for aircraft. Active noise canceling circuits typically invert unwanted noise signals by filtering out ambient noise signals with noise canceling microphones. This is applied to the receive channel and subtractively interferes with the noise signal. However, the difficulty of handset design incorporating electronic cancellation techniques is in part related to the matching of the acoustic characteristics of the handset, specifically the phase and amplitude of the noise canceling signal to the noise itself. The handset should be designed to have an amplitude and phase response that matches the actual control circuitry for noise cancellation.

According to the invention, there is provided an ambient noise reduction telephone handset as claimed in claim 1. The earpiece of the earpiece cap was formed as a central opening in which the housing was installed. This housing includes a noise canceling microphone. A portion of this housing extends out of the earpiece to fit into the user's outer ear. Thus, the microphone directly samples ambient noise near the user's ear hole. The noise canceling circuit responds to ambient noise by generating a noise reduction signal that is optimally phase related to the ambient noise signal.

The noise canceller of the present invention is shown in the telephone handset 10 in FIG. The handset 10 is basically in a conventional configuration and includes a handset cap 11 and a handset cap 12. An acoustic blocking foam 13 is disposed in the handle portion 14 of the handset 10. The foam 13 may be composed of a material such as open pore polyurethane, which has significant elasticity, good compliance and high acoustic damping properties. The foam 13 is an integral part of the acoustic circuit in order to reduce as much as possible the user's own voice energy transferred from the handset's handset to the handset. The foam 13 also suppresses acoustic resonance in the handset by effectively controlling the space behind the receiver.

As shown in Figs. 2 and 3, the handset cap 12 is connected to the telephone line 9 of the communication network by a wire 16 via a noise canceling control circuit 40. ). The earpiece 15 is housed in a speaker mounting sleeve 17 suitably fitted in an annular housing 18 of the receiver cap 12.

The earpiece cap 12 is fabricated with an earpiece 19 that is slightly rounded on the outer surface 20 in contact with the user's ear. The series of radial slots 21 shown in FIG. An acoustic grill is provided, through which the incoming signal from the handset 15 reaches the ear hole of the user. The slot 21 is also configured and arranged to allow voice to pass along the shortest possible path from the earpiece 15 to the microphone 22 disposed in the microphone housing 23.

The microphone housing 23 includes a flange 24 for positioning the housing 23 on the outer surface 20 and a sleeve 25 in which the microphone 22 is fixedly installed. The housing 23 also includes a series of voice ports 26 formed through the extension 27 of the housing 23. The extension 27 slightly enters the user's outer ear to assist in positioning the receiver relative to the user's ear, and places the microphone 22 as close to the ear as possible to detect the correct voice distribution heard in the user's ear. This match is necessary to achieve optimal noise canceling performance over a bandwidth of about 100 Hz to 1000 Hz, which is most important for control to improve speech clarity.

In addition, as shown in FIGS. 2 and 3, the voice port 26 is coupled to the acoustic grille slot 21 to form a short and direct voice path between the microphone 22 and the receiver 15, thereby providing a relatively acoustic resistance. And virtually no phase delay. In order to minimize the phase delay between the control signal received by the microphone 22 and the noise canceling signal generated in the circuit 40, it is highly desirable to minimize the acoustic resistance between the handset 15 and the microphone 22. These control signals and noise cancellation signals should be as little as possible in phase difference. 3 shows the voice port 26 and the possible long voice grill slot 21, which are essentially arranged in close proximity to each other.

The microphone wire 32, which connects the microphone 22 to the control circuit 40, may come out of the cavity 29 through a passage 33 formed in the annular housing 18. Preferably, a felt pad 28 is disposed between the microphone 22 and the voice port 26 to prevent dirt and other particles from entering the microphone 22 through the port 26. A layer of acoustically transmissible material may be added on top of the pad 2 to more reliably prevent the ingress of dust and moisture. The acoustic slot 21 should likewise not be opened to allow particulates to enter or paper clips or the like into the receiver cap. The protective screen 31 is preferably arranged on the handset 15. The screen 31 may be a perforated metal disk or grill. Acoustically, the screen 31 serves to convey the voice from the handset 15 without distortion or reduction.

As shown in FIG. 2, the handset cap 12 includes a cavity 29 in which the foam 30 is located. The foam 30 preferably has an open cell structure and is light in weight. Reticulated polyurethane foam is one of the suitable materials. The foam 30 prevents foreign matter from entering the receiver 15 and smoothes the phase responsiveness by attenuating undesirable resonance modes and reflective components from the enclosure or the user's ear.

The residual phase delay between the noise canceling signal driving handset 15 and the control signal occurring in the microphone 22 may be predetermined.

The handset design of the present invention creates an electroacoustic transfer function from the speaker input voltage to the microphone output voltage and adds a low complexity compensation circuit to provide excellent closed loop cancellation performance in the range of 100 Hz to 1100 Hz. This transfer function, shown in Figure 4, provides several important features. First, its transfer function gradually changes with frequency without being irregular or with peak response portions. In addition, the magnitude of the transfer function drops sharply at frequencies above about 1000 Hz so that almost all resonance peaks above about 2000 Hz are substantially 20 dB above the maximum amplitude. In addition, the phase of the transfer function is in the range from 0 ° to 360 ° in the range from about 100 Hz and above 3000 Hz, as can be seen from the curve shown at the bottom of FIG. The physical design concept of the present invention helps to achieve these results.

Importantly, the size and shape of the slot 21 and port 26 should be controlled to prevent acoustic resonance of the microphone 22 and the receiver envelope. The space enclosed by the microphone housing 23 associated with the port 26 and the microphone 22 includes a potential resonance acoustic chamber. The resonance response of such chambers at frequencies within the audible frequency range will result in amplitude and phase response distortions that degrade acoustic noise reduction performance. The configuration, diameter and length of the port 26 were chosen to reduce the distortion effects described above. The same undesirable resonant effect is eliminated in the receiver enclosure by the formation of a slot 21 which prevents access to the speaker while passing the voice.

The utility of the present invention can be further confirmed with reference to FIG. 5. The data for noise cancellation versus frequency obtained from experiments on a single subject are for the present invention used with complementary noise cancellation compensation circuits. Noise cancellation is the ratio of the noise power spectrum when the cancellation circuit measured in dB at the user's ear is “off” and the noise power spectrum when the cancellation circuit is “on”. It may be prescribed. This measurement was done using an Etymotic ear probe with a spectrum analyzer in the subject's eardrum. 5 shows noise cancellation performance over a range of 100 Hz to 1100 Hz, with noise cancellation performance reaching more than 10 dB in the range of 130 Hz to 700 Hz and up to 15 dB at 400 Hz. This offset frequency band is very effective in the typical noisy environment mentioned above. This noise cancellation level is sufficient to allow for other ambiguous incoming voices.

Claims (8)

A handset, a handset, a handset and handset caps 11 and 12 disposed on the handset and the handset, respectively, a handset 15 mounted in the handset cap 12, a noise canceling microphone 22, In the ambient noise reduction telephone handset 10 comprising a noise cancellation control circuit 40 and means 32 for connecting the microphone 22 to the circuit 40, The earpiece cap 12 comprises an earpiece 19 with a central opening formed on the outer surface 20, The housing 23 mounted through the opening and extending into the cap 12 toward the receiver 15 receives the microphone 22, The housing further includes an extension 27 protruding outward, which extension fits into the user's outer ear to directly direct ambient noise where the microphone 22 is closest to the user's ear hole. Ambient noise reduction telephone handset, characterized in that for positioning the microphone (22) for sampling. The method of claim 1, A plurality of radial slots 21 arranged around the opening through the earpiece 19 to define an acoustic grill through which the signal from the earpiece 15 is substantially transmitted directly to the ear hole of the user. Ambient noise reduction telephone handset, including more. The method of claim 2, The housing extension 27 includes a plurality of voice ports 26, which are configured and sized to reduce the resonant response characteristics of the microphone housing 23. . The method according to claim 2 or 3, Ambient noise reduction telephone handset, further comprising an acoustically transmissive pad 28 disposed between the microphone 22 and the port 26 to block particulates entering the receiver cap through the port 26. . The method of claim 4, wherein Ambient noise reduction telephone handset further comprising a layer of acoustically permeable dust and a moisture-impermeable material disposed on an outer facing surface of the pad (28). 6. An acoustic non-distortion protective screen (31) according to claim 5, further comprising an acoustic non-distortion protective screen (31) disposed on an outer facing surface of the receiver (15) to pass voice from the handset (15) with minimal distortion and energy loss. Ambient Noise Reduction Telephone Handset. The method of claim 6, The handset cap 12 further comprises an open cell foam 30 received in a space between the handset 15 and the microphone 22, the foam 30 having an interior space of the cap 12 and Ambient noise reduction telephone handset, suitable for attenuating resonance modes and reflections from the user's ear. The method of claim 6, The screen (31) comprises a perforated metal disk of the ambient noise reduction telephone handset.